A thermal fixing device for an electro-photographic type image forming device including a tubular fusing film, a heater disposed at a space defined in an inner peripheral surface of the fusing film, a pressure roller, and a nip plate defining a nip region in cooperation with the pressure roller through the fusing film, and a stay supporting the nip plate is known. Further, the fixing device includes a reflection plate disposed at a rear side of the heater to reflect radiant heat from the heater to the nip plate. In the fixing device with this configuration, the nip plate can be efficiently heated by the radiant heat from the heater.